Signaling system for railroads



Nov. 5, 1946. T. J. JUDGE SIGNALING SYSTEM FOR RAILROADS Filed May 1,1944 5 Sheets-Sheet 1 v Central Offce Motor Car Indicator T. J. JUDGE2,410,504 SIGNALING SYSTEM FOR RAILROADS 7 Filed May 1, 1944 5 Sheets-Sheet 2 FIG-.15,v

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T. J. JUDGE S'IGNALING SYSTEM 170R RAILROADS Filed May 1, 1944 5Sheets-$heet 4 LGT Nov. 5, 1946. UDGE 2,410,504,

SIGNALING SYSTEM FOR BAILROADS Filed May 1, 1944 5 Sheets-Sheet 5 FIG.2.

Lil I125 T56 i 59 l lnventor Patented Nov. 5,1946

SIGNALING SYSTEM FOR RAILROADS Thomas J. Judge, Rochester, N. Y.,assignor to General Railway Signal Company, Rochester,

Application May 1, 1944, Serial No. 533,493

14 Claims.

i This invention relates to railway signaling systems, and moreparticularly to a signaling system for governing the movement of tramcover stretches of single track over which traffic may move in bothdirections.

Single track railroads are ordinarily provided with signaling systems ofthe absolute-permissive-block type in which trains may move in only onedirection in a single track stretch at any one time, but where followingtrains are permitted to move under the usual three indication signalingwhere clear,'caution and stop indications are provided. In other words,an absolute-permissive-block (APB) signaling system prevents theentrance of all opposing trains into the single track stretch when it isoccupied but permits following train movements with the usual blockspacing. In a single track railroad provided with centralized trafllccontrol, the APB signaling is organized so that the head-block signals,that is, the signals governing the movement of traffic into the singletrack stretches, and the entering signals, that is, the signalsgoverning the entrance of trafiic into the siding sections from a singletrack stretch, are normally held at stop, but may be cleared in responseto manual control subject to the automatic signaling circuits.

In such a system where centralized trafflc control is employed with APBsignaling, it is considered desirable to check all opposing signals atstop before the signals for the desired direction are permitted toclear. Thus, one object of the present invention is to provide a systemof signaling wherein" the opposing signals are checked at stop beforethe signals of the desired direction can be cleared together with theprovision of means which prevents the interruption of an signallocations which are caused to indicate.

when opposing traffic is established to warn workmen against proceedinginto .the single track stretch against the established direction oftrafiic.

A still further object of the present invention is to provide motor carindicators associated with each of the intermediate signal locations aswell as the head-block signal locations when the usual track circuitcontrolled approach lighting is employed.

Other objects, purposes and characteristic features of the presentinvention will be in part pointed out in the following description andwill be in part obvious from the accompanyin drawings.

. In describing the invention in detail, reference will be made to theaccompanying drawings, in which like reference characters provided withdistinctive preceding numerals designate corresponding parts throughoutthe several views, and in which Figs. 1A, 1B, 1C and 1D when placed sideby side represent one form of signaling system provided by the presentinvention; and

Fig. 2 illustrates a modified form of the circuit organization shown inFig. 13 to illustrate a modified form of. the present invention wheremotor car indicators are employed at intermediate signal locations whenconventional track circuit controlled approach lighting is employed.

For the purpose of simplifying the illustrations.

parts and circuits constituting the embodiment of the invention havebeen shown diagrammatically established route by the manual control atthe leaving end of the route. It is also proposed that this shall beaccomplished over a, minimum number of line wires, such as the threeline wires disclosed in the present application as including two controllines and a common return line, such line wires being individual toeach'block of the single track stretch.

A further object of the invention is to provide means for lighting thesignals only when a route is established so as to conserve both theequipment and energy that would otherwise be used if the signals werecontinuously illuminated. It is further desired to effect thislightingof the signals to forewam workmen of the contemplated passage ofa train in a given direction.

A further object of the invention is to provide so-called motor carindicators at the head-block and certain conventional illustrations havebeen employed, the drawings having been made more with the idea to makeit easier to understand the principle and mode of operation, than withthe idea of illustrating the specific construction and arrangement ofparts that would be employed in connection, it is to be understood thatthese symbols represent different and separate sources for the differentsignal locations shown in the several a figures of the drawings, thatis, each of the Figs. 1A, 1B, 1C and ID are provided with separatebatteries or other sources of direct current. This is pointed out so asto make clear that the same instantaneous polarities.

General organization With reference to Figs. 1A, 1B, 1C and 1D placedside by side, it will be seen that a stretch of single track has beenshown extending between two passing sidings A and B. These passingsidings are connected to the main track by the usual power operatedtrack switches. In Fig. 1A, the track switch 9T8 is shown as connectingthe passing siding A'to the main track when in a reverse position, andthis tracl; switch STS is operated to its normal main line position andto its reverse position by a poweroperated switch machine 98M.Associated with this switch is the usual detector track section 9Tnormally energized by a suitable track battery for maintaining energizedthe track relay 8TH. except when a train is present in such tracksection.

Similarly, the track switch HTS of Fig. 1D provides for main line orpassing siding trafilc in accordance with its normaland reversepositions respectively as provided by the power operationof switchmachine I'ISM. An associated detector tracksection "T with the usualtrack battery is provided for energizing its associated track relay IHR.

The head-block signals IA and 1B of Fig; 1A are provided for governingeastbound tramc over the single track stretch, while the head-blockvided for governing westbound traffic over the a main track or on to thepassing siding A; while the entering signals ISA and I53 are provided togovern eastbound traihc over the main track or on to siding B as thecase may be.

In Fig. 13, a double intermediate signal location is illustrated asincluding signals H and I2 for eastbound and westbound treficrespectively; while in Fig. 1C a single intermediate signal location isshown having the signal II for governing westbound traflic.

The single track stretch is of course divided into track sections ortrack circuits of the usual or conventional type where a so-calledcut-section is provided at some intermediate point supplied with energyat such cut-section for energizing the track relays at the opposite endsof the section adjacent the signal locations. These cut-sections havebeen given reference characters bearing the same preceding numeral asthe signal with which they are immediately associated, These tracksections or blocks between pairs of signals may have coded trackcircuits applied thereto, in which case cut-sections are not usuallyrequired. In other words, it should be understood that any suitable typetrack circuits maybe employed in which there is train detecting meansadjacent each end of theblock to effect the principles of operation ofthe present invention.

For convenience in the illustration, the signals have been shown asbeing of the multiple aspect Searchlight type signal, such as shown, forexample, in the Patent No. 1,835,150, granted to O. S. Field, December8, 1931, but it is to be understood that any other suitable signal mightbe employed and still practice the principles of the present invention.Each of these light signals has a movable spectacle which is normallybiased to its center position in which the signal displays a stop or redindication when illuminated; but

the signal displays a green or yellow indication when such spectacleis,mov,ed to one or the other extreme position respectively. Thismovement of the spectacle is also used to operate contacts whichnormally assume the positions shown, but when the spectacle is operatedto the right, the left-hand contact assumes its dotted line position,but when the spectacle is operated to the left the right-hand contactassumes its dotted line position. These contacts are employed to providefor the energization of the usual red repeating relays RP and theyellow-green repeating relays YGP. These relays are of course suppliedwith suitable distinctive preceding numerals to indicate the particularsignal with which they are associated.

The red repeating relays, such as relay lRP, are normally energized withthe associated signals at stop, but are deenergized whenever anassociated signal is causedlto give :3. proceed indication, eitheryellow or green. The yellowgreen repeating relays, such as IYGP, arecontrolled so as tobe energized whenever the associated signal is causedto indicate yellow or green. However, it should be noted that this iswith respect to the main signal only, since the automatic blocksignaling is provided for the main track. For example, the clearing ofthe signal 'IB does not provide for the energization of the relay 'IYGP,since there is usually no automatic signaling associated with the sidetrack. Similarly, the clearing of the turn out signal 83 does not causethe energization of the relay BYGP because a high speed indication undersuch circumstances should not be given by the signal 12 since the routeis a low speed route over the track switch STS in its reverse position.

In thespecific form shown, Searchlight typesignals are employed wherethe operating windings actuate both signal aspects and relay con-- case,only a suitable relay structure is necessary I to be controlled the sameas each signal shown, and the contacts of such relay structure can be.used to control the color lights of the signal.

This is pointed out since it is convenient in .the claims to considerthe signals as relays, which they are, so as to generically recite theessential elements ofthe present invention without specitying the typeof signals to be used.

Although power operated switch machines SM have been indicated asassociated with the track switches TS, no manual control has been shownfor such switch machines, since this control may be of any desired type,such as disclosed for example in my prior application, Ser. No. 455,922,filed August 24, 1942, now Patent No. 2,350,620, dated June 6, 1944.Such control wou d of course include suitable detector and approachlocking means, such as shown insaid prior filed application. However, itis believed that all such switch machine control is unnecessary for anunderproach locking stick relays AS have been shown in block form inFigs. 1A and 1D to indicate their relationship to the circuits of thepresent invention. For example, it is only necessary to understand thatthe relay 'IAS is deenergized whenever the signal IA or 1B is caused toindicate clear and this relay IAS remains deenergized for apredetermined measured time subsequent to the restoration of suchsignals to their stop displaying positions.

Also, a switch position repeating relay WP of the usual polarized typeis shown associated with each of the switches. For example, the relay9WP is indicated as a polar neutral rela-y controlled to a normalenergized position with the track switch 9TS and switch machine QSM innormal locked positions, and is controlled to a reverse energizedposition with the track switch 9TS and switch machine 98M in reverselocked positions, but is deenergized whenever the track switch 9TS orswitch machine 98M becomes unlocked. Suitable correspondence repeatingrelays would probably be employed with such switch position indicatingrelay, but these have not been shown for the sake of simplicity in theillustration of the present disclosure.

Extending between each of the signal locations of the single trackstretch are three line wires, two of which are used as control lines andthe ,third wire being used as a common return. These line wires areindividual to each of the sections of track or blocks between two signallocations and" serve for controlling the home-distance relays HD orsignal operating windings at each end of the section as well as thetraific' locking relays BK and CK. Certain of the home-distant relays HDare provided with direct repeating relays of the slow acting type giventhe reference characters HDP.

At each head-block signal location the entering and head-block signalsare shown as being held .at stop by suitable manual control which takesthe form of amanually controlled relay GZ that may be controlled in anysuitable manner from a central oflice by either direct line wire controlor a suitable code type communication system, This manually controlledrelay GZ has associated with it a repeater relay GZP which can repeatits energization subject to certain traffic conditions indicating thatit is proper for the newly desired route to be'established.

Associated with each head-block signal as shown in Figs. 1A and ID, aresuitable motor car indicators so designated by their respective legends,which indicators ar illuminated only when it is safe for a motor car orworkmen to proceed over the track into th single track stretch fromtheir respective head-block signal locations.

This form of control is provided so as to give an indication on the sideof safety, since a burned-out lamp corresponds to the most restrictiveindication which th indicator can give.

are provided at each signal location which will be illuminated when aroute is established even though the signals themselves are notilluminated until a train approaches. This form of motor car indicatorfor an intermediate signal is particularly useful on railroads where thesignal itself cannot be seen around a curve sulficiently far to giveproper warning to a motor car, and in such a case the indicator would belocated at a proper point in approach to the curve and its controlextended from the intermediate signal.

Operation The system is organized to have a signal clearing tumble-downcircuit for each direction of trafilc with these tumble-down circuitsinterlocked in such a way that the signals can,be cleared for eitherselected direction only providing the signals for the opposite directionare at stop. In addition to these signal clearing tumble-down circuits,a traffic locking tumbledown circuit is also provided for each directionof trafiic, and thes traific locking tumble-down circuits aresuperimposed upon the'signal clearing tumble-down circuits in a mannerto avoid the use of additional line wires.

Under normal conditions when no route is established, both the signalclearing tumbledown circuit for the last direction of trafiic and thetrafiic locking tumble down circuits for the opposite direction areenergized. Since both signal clearing and traffic locking tumble-downcircuits are subject to manual control exercised r at the ends of thesingle track stretch, the energization of the GZ relay at eitherselected end of the stretch in response to manual control causes thedeenergization of the particular tum ble-down circuit then energizedfrom that end and relating to the opposing direction of traiflc.

With more specific reference to the Figs. 1A, 1B, 1C and 1D, the lastdirection of traflic movement was from left to right so that the signalclearing tumble-down circuits for the signals 1A and II are energized,while the traffic locking tumble-down circuits for signals Hi, It and I2are also energized. Thus, if the relay 'lGZ is picked up, then itsrepeater relay lGZP is energized and opens a back contact for causingthe deenergization of the traffic locking tumble-down circuits includingrelays IZBK, IQBK and lGBK.

On the other hand, if the relay IGGZ .is ener- -gized, instead of relay'IGZ, then the relay IBGZP the tramc locking tumble-down circuits forthe signals H and i would remain deenergized.

It can thus be seen that the signals are so controlled that the opposingsignals must be at stop before the signals for particular direction canbe cleared and that the deenergization of the traiilc lockingtumble-down circuit, which is of course deenergized for the opposingdirection of trafiie at the same time that the signal clearing controlis set up, prevents the manual control of a GZ relay at the opposite endof the singl track stretch from being effective to pick up its repeatingrelay and thus interrupt the established direction of trafilc. Thetrafiic looking tumble-down circuits are thus used to lock carindicators.

the established route and at the same time provide approach lightingcontrol for the intermediate signals as well as control for the motorWith this general discussion of the operation of the system, it isbelieved that further discussion' should be given with respect to thespecific circuits and operations involved in the system.

Normal conditions.As above mentioned, the track circuits are normallyenergized so that their respective track relays TR are picked up. Also,the approach locking stick relays, such as relays 1AS, 8AS, iSAS andIGAS, shown in block form, ar also normally energized, as explained indetail in my prior application Ser. No. 455,922, filed August 24, 1942.

All of the signals are unilluminated except the head-block signals 1A,1B, ISA and 16B, and these signals are continuously illuminated so thata train standing on the siding where no'track circuits are provided,will be advised as to the traffic controlling conditions. As abovementioned,

the last movementsof trailic was from left to right, and this leaves thesignal clearing tumble-down circuit for the signals 1A and II energized.Since the signal. location of Fi 1C is shown as a single intermediatesignal location, the signal circuit for signal II is controlled to acaution condition, but it is to be understood that if a doubleintermediate signal location were provided in Fig. 1C, that such signalgoverning traffic toward the siding B, would indicate caution in therear of the signals ISA and B, and that the signal Ii would then becontrolled to its clear or green indicating position. It of courseshould be understood that this control is present although the signalsare not-illuminated.

With this general understanding of the signal clearing tumble-downcircuits for the eastbound signals, a specific description of eachcircuit in-. volved will now be given.

The relay |3HD (which has no associated intermediate signal) isenergized by a circuit closed from and including back contact 20 ofrelay I5YGP, front contact 2| of track relay IG'I'R, common line wire 22to the signal location of Fig. 1C, front contact 23 of track relay l3TR,windings of relay I3HD', back contact 24 of relay us, back contact 25oirelay MYGP, front consignal I I is energized so as to actuate itsmovablespectacle to a caution or yellow indicating position, and thisenergizing circuit, may be traced from through a circuit including thecontacts 35 and 35 ofsignal H at stop positions (see Fig. 1C), polarcontact 31 of relay i3HD in a right-hand position, front contact 38 ofrelay I3HDP, back contact 39 of relay l3BK, front contact ll! of relayTR, line wire 41 to the signal location of Fig. 1B,front contact 42 oftrack relay l ITR, through the operatin winding of signal ll, backcontact 43 of relay IZS, back contact 44 of relay I2YGP, front contact45 of relay HTR, line wire '46 to the signal location of Fig. 1C, frontcontact 41 of track relay TR,

back contact 48 of relay MS, back contact 49 of relay HYGP, frontcontact 50 of relay I3HDP, polar contact 5! of relay I3HD in aright-hand position, to The current which flows in this circuit actuatesthe signal II to its caution indicating position, which closes anenergizing circuit for the the relay HYGP from and including contact 52of signal H in its normal position, contact 53 of signal H in anoperated position, front contact 98 of relay IZTR, windings of relayIIYGP, to

The energization of this relay HYGP with the signal l2 at stop completesa circuit for the relay 1HD and including signal contacts 19 and 55 ofsignal 12 in normal stop positions, front contact 55 of relay HYGP, backcontact 51 0i relay I2YGP, back contact 58 of relay I2S, front contact59 of relay IZTR, line wire 60 to the signal location of Fig. 1A, frontcontact 6| of relay 1TR, back contact 62 of relay 1CK, windin s of relay1HD, frontcontact 63 of relay 1TB, line wire 54 to the signal locationof Fig. 13, front contact 65 of track relay I2'I'R, front contact 65 ofrelay IIYGP, to The current which flows in this circuit is of such adirection as to operate thepolar contacts of relay 1HD to theirleft-hand positions and to close the neutral contacts of this relay. Theclosure of front contact 51 of relay II-ID energizes the repeater relay1HDP through an obvious circuit.

The closure of front contact 68 of this relay- 1HD completes an obviousenergizing circuit for the motor car indicators, thus giving anindication to a motor car operator or to other workmen that there is noopposing traflic and that it is saie'to proceed in an eastbounddirection over the single track stretch.

Under these normal conditions the traffic locking tumble-down circuitsfor the opposing direction are energized. More specifically, the relayI2BK of Fig. 1B is energized by a circuit closed from and includingcontacts 19 and 55 of signal 12 in their stop positions, front contact56 of relay HYGP, windings of relay I2BK, front contact 10 of relayIIYGP, front contact 11 of track relay IZTR, line wire 12 to the signallocation of Fig. 1A, front contact 13 of relay 1AS, front contact 14 ofrelay 1'I'R, front contact 15 of relay STR, back contact 16 of relay1GZP, front contact 11 of relay 1HDP, front contact 63 of relay 1TB,line wire 64 to the signal location of Fig. 13, front contact 65 ofrelay IZTR, front contact 66 of relay IIYGP, to

It will be noted that this energization of the relay IZBK is from asource of energy located at the signal location of Fig. 13 instead ofthe signal location of Fig. 1A as might be expected for tumble-downcircuits. This relationship of they relay IZBK with respect to itssource is provided so as to prevent any erroneous energization of relaysat the head-block signal location of Fig. 1A upon a reversal ofthe'direction of the signal control, as will be mentioned more in detaillater. However, it will be mentioned here, that the traffic lockingtumble-down circuits with respect to the plurality of intermediatesignals are arranged to have the source at one signal location and theindicating relay such as BK at the other signal location, as shownbetween the signal locations of Fig. 1B and 1C.

The energization of the relay I2BK provides that the relay HBK of Fig.1C is energized over .a circuit closed from and including contact 52 ofsignal I! in a normal position and contact 53 of signal H in an operatedposition, front'contact 54 of relay I2BK, front contact 42 of relayIITR, line wire 4| to the signal location of Fig. 10, front contact 48of relay MTR, windings of relay HBK, front contact 80 of relay I3HDP,

, This energization of the relay MBK permits p the energization of therelay IBBK of Fig. ID by reason of a circuit closed from and includingback contact 20 of relay ISYGP, front contact 2I of relay IGTR, linewire 22 to the signal location of Fig. 1C, front contact 23 of trackrelay I3TR, front contact 81 of relay I IBK, front contact 88 of relayI3HD, front contact 89 of relay I3HDP, front contact 98 of track relayI3TR, line wire 9i to the signal location of Fig. 1D, front contact 92of track relay I6TR,-front contact 93 of relay IBCK, windings of relayISBK, back contact 33 of relay ISYGP, to I The energization of thisrelay IBBK closes front contact 98 to energize the motor car indicatorby an obvious circuit which gives an indication to a motor car operatoror other workmen that conditions are not set up for eastbound traffic,thus making it safe for westbound movement into the single trackstretch.

With a tumble-down circuit normally energized for each direction, itwill be presently explained.

how the exercise of manual control at either selected end of the singletrack stretch will result in the establishment of a route for trafllcmovement away from that end and at the same time approach lighting thesignals of the stretch and acting to prevent accidental manual controlat the otherend from interrupting the established route.

Manual signal clearing for eastbound flame.- Let us assume that theoperator desires to clear signal IA and by, suitable communication meanseffects the energization of the relay IGZ. This picking up of relay 'IGZcloses a pick-up circuit for the relay IGZP from and including frontcontact 98 of relay IGZ, front contact 98 of'relay IHD, windings ofrelay 'IGZP, to As soon as the relay 'IGZP picks up, it closes frontcontact 91 to complete a stick relay wholly dependent upon the continuedclosure of front contact 95 of relay 162.

Since the previously established route was for eastbound trafllc, therelay IHD is already energized, and a circuit for immediately clearingthe signal 1A is closed from(+) and including front contact I 80 ofrelay 8A8. front contact IBI of relay 9TB, front contact I02 of relay'IGZP, front contact 188 of relay 'IHD, front contact I88 of relay 9WP,polar contact I ofrelay 9WP in a left-hand normal position, polarcontact I88 of relay IHD in a left-hand position, operating winding ofsignal IA, polar contact I81 of relay 'IHD in a left-hand position, to(-,--l. The energy which flows in this circuit is of such a direction byreason of pole changing contacts I86 and III! of relay IHD, that thesignal IA is operated to its clear or green indicating position and suchan indication is immediately displayed because its lamp is continuouslylighted.

At the same time that relay 'IGZP effects this signal clearing control.the traffic lockin tumble-down circuit for the Opposing direction oftrafllc is deenergized by reason of the opening of back contact 16 ofrelay IGZP which 'deenergizes the circuit for the relay I2BK of-Fig. 1B;the

opening-of contacts 54 and 88 of this relay I2BK also deenergizes thecircuit forthe relay I IBK of Fig.1C; and thisrelay MBK in turn opensfront contact 87 to deenergize the relay IBBK of 5 Fig. 1D.

Referring to Fig. 1D, the opening of front contact I88 of relay IIiBKentirely opens thepickup circuit for the relay IBGZP. Thus, it will beapparent that any unintentional or accidental control of 'the relayIBGZ, cannot result in the picking up of the relay IGGZP and thus breakthe energized signal clearin tumble-down circuit governing eastboundtraffic by the opening of back contact 3I.

The opening of front contact 93 of relay ISBK also extinguishes theillumination of the associated motor car indicator and advises workmen.that opposing trafllc has been established,

The deenergization of the traffic locking t'umble-down circuit includingrelays I3BK, I 613K and ISBKalso effects the lighting of theirrespective-signals. More specifically, in Figs. 1B, the closed conditionof back contacts I I8 and III of relay I2BK and IIBK respectively,completes obvious energizing circuits for the lamps of signals I I andI2 in multiple. Similarly, the closed condition of back contacts H2 andH3 (see Fig. .10) of relays ISBK and ItBK respectively, completes anobvious energizing circuit for the lamp of signal It. Also, the closedcondition of back contacts H5 and IIS of relays IBHDP and IBBKrespectively, completes the energizing circuits for the lamps of signalsISA and I5B in multiple. Although these signals are assumed to be atstop in the prior description of the signaling circuits, it is to beunderstood that they can be manually cleared subject to suitableautomatic signaling circuits (not shown) for the main track through thesiding section,

Before considering how manual control can be exercised at the signallocation of Fig. ID by the picking up of relay IBGZ and thus establishwestbound traffic, it appears to be expedient to first consider theoperation of the system upon the passage of an eastbound train throughthe single track stretch. Passage of an eastbound train.-Let us assumethat a train accepts the clear signal Hi and proceeds into the detectortrack section 9T, this opens front contact Illi of the track relay 9TBincluded in the circuit for signal 1A and thus causes it to go to stop.At the same time, front contact I5 of relay 9TR is opened, so that thetraffic locking tumble-down circuit for the opposing direction oftraffic cannot be reenergized even though the operator might restore therelay 'IGZ to its deenergized position which would result in thedeenergization of the relay 'EGZP and closure of the back contact l6. Inother words, the presence of the train in the detector track section 9Tcontinues the locking condition for opposing traffic that has beenestablished bythe picking up of the relay 'IGZP.

Assuming that the train proceeds into the track 05 section includingtrack circuits IT and I2T between thehead-block signals and the signalI2, the track relay 'ITR is first deenergized opening front contacts 8!,83 and It and is then followed by the deenergization of track relayI2'I'R open-- 70 ingthe front contacts 98, 59, and H, thus continuingthe open condition of the line circuit for the traffic lockingtumble-down circuit. It will be noted that the opening of front contact8| of track relay ITR, and also the continued 7 opening of such linecircuit by opening front .contact 59 of relay IZTR causes'thedeenergization of the relay IHD so that the signals IA and IB aremaintained at stop by open front contact I03 although the track relay9TB is reenergized' closing front contact IOI- when the train leaves thedetector track section 9T.

When the train deenergizes the track relay I2TR, a pick-up circuit forthe directional stick relay MS is closed from and including contact 52of signal II in a normal position, contact 53 of signal H in an operatedposition. back contact 98 of track relay .I2TR. front contact I20 ofrelay IIGYP, windings of relay IIS, to The deenergization of the trackrelay IZTR opens front contact 98 so that the relay IIYGP is deenergizedafter a period of time measured by its slow releasing characteristicsopening front contact I20 included in the pick-up circuit for II S, butthis does not affect the continued energization of relay -i IS sincefront contact I2I of relay HS completes a stick circuit which receivesenergy directly from the contacts 52 and 53 of the signal I I Upon theclosure of back contact I20 of relay IIYGP, energy is applied directlyto the stick circuit of the relay IIS so that the restoration of thesignal i I to stop when the train way cause the release of the stickrelay IIS.

When the train has proceeded past the signal I I and caused it to beplaced at stop by reason of the open condition of front contacts 42 and45 of the track relay IITR, the directional stick relay I IS closes anenergizing circuit for the relay IHD from and including contacts I9 and55 of signal I2 in their normal stop positions. front contact I22 ofrelay IIS, back contact 66 of relay IIYGP, front contact 65 of relayI2TR, line wire 64 to the signal location of Fig. 1A, front contact 63of track relay ITR, windings of relay IHD, back contact 6201 relay 'ICK,front contact SI of relay 'ITR, line wire 60 to the signal location ofFig. 13, front contact 59 of track relay i2TR, back contact 58 of relayI2S, back contact 51 of relay IZYGP, back contact 50 of relay IIYGP,

' front contact I23 of relay IIS, to The enmay be actuated to a cautionor yellow indicating position in response to manual control. In otherwords, a following train movement is permitted in the rear of the trainwhich has now passed the signal II.

Since there is no intermediate signal at the location of Fig. 10, thereis no directional stick relay provided. Thus, the opening of the frontcontacts 26, 23 and 90 of the track relay. i3TR deenergizes the relayI3HD which continues the signal II at stop and which in turn merelypermits the signals IA or IE to be operated to their caution indicatingpositions. However, when the train has passed beyond the detector tracksection IIT into the passing siding or into the main track section, therelay I3HD is reenergized and thus restores the signal II to its cautionindleating position which in turn will permit the si nals IA or IE to becaused to indicate clear or green in response to manual control,

It will be noted that the directional stick relay H8 is maintained stuckup until the signal II is restored to its caution indicating conditionresulting in'the picking up of the relay IIYGP and the opening of thestick circuit for the relay H8 at back contact I20. This occurs when theeast- I bound train passes out of the single track stretch.

, passes into the track circuit lIT does not in any Inasmuch as therelay IGGZP cannot be picked up in response to manual control until thetrafllc locking relay ISBK has been reenergized, which in turn isdependent upon the signal clearing tumble-down circuit for eastboundtraffic, the release of the directional stick relays (such as relay HS)associated with the'signals for eastbound traflic is assured. In otherwords, the directional stick relays for either direction are assured ofrelease because of the sequence in which the. tumble-down circuits mustbe restored to their conditions established prior to the entrance of atrain before the direction of traffic can be reversed.

Approach locking contrcl.It should be noted that once a route has beenestablished by the clearing of ahead-block signal, the reversal oftrailic direction in the single track stretch is prevented for apredetermined time after such headblock signal is restored to stop, if atrain is approaching such signal. This feature is provided so as to givea train approachin the signal IA.

' for example, suiflcient time to come to stop upon the restoration ofsuch signal to stop in the face of that train, or to allow the trainsufliclent time to enter the detector track section and by its presenceprevent the reversal of trafllc in the single track stretch. If thereversal of traffic IA. This might result in two trains entering thesingle track stretch at the same time, which is obviously undesirable.

Thus, the present invention provides that the approach locking stickrelay IAS has a front contact 13 included in the traffic lockingtumbledown circuit so that such trafllc locking tumbledown circuit willnot be energized upon the closure of the back contact I6 until apredetermined time after the signal IA or IE has been restored to stop.Thus. the traffic locking relay ISBK at the opposite end of the stretchremains deenergized preventing the manual control of the relay IGGZP forthe time measured by the approach locking time measuring relay, asdisclosed in my-prior application Ser. No. 455,922, filed August 24,1942.

Similar control is of course, provided at the opposite end of thestretch indicated in Fig. ID by the provision of the approach lockingstick relay IBAS.

ill)

The signals IA and 1B are similarly held at stop for a predeterminedtime after the signals 8A or 03 have been cleared and restored to stop.This is accomplished by the inclusion of front contact I00 of the relay8A5 in the signal controlling circuit, since this approach locking stickrelay 8A8 is deenergized for a predetermined time subsequent to therestoration to the stop of the manually controlled signals 8A and 83.

Manual control for westbound flame-Let us assume that the system is inthe'conditlon illustrated, and that the central operator desires toallow a train'to pass from the siding B into the single track stretchtoward the siding A. To do this he first controls the track switch IITSto a reverse position by the proper control of switch machine ISM, whichcauses the switch position indicating relay IWP to be energized with theopposite polarity when the track switch "TS is in its reverse lockedposition. Manual control is then exercised to energize the relay IGGZthus completing a pick-up circuit for the relay I SGZP from through acircuit including front contact I24 of relay IGGZ, front contact IIl8 ofrelay IGBK, winding of relay IGGZP. to As soon as this'relay IIiGZPpicks up and closes front contact I25, an obvious stick circuitis'closed rendering the relay IGGZP wholly dependent upon the energizedcondition of relayIBGZ.

The opening of back contact 3| of relay IGGZP causes the deenergizationof the relay I3I-ID followed by the restoration of'the signal II to itsvstop condition. The restoration of signal II to its stop condition movescontact 53 of signal II time that therelay 'IHD is deenergized. Thenafter a period of time measured by the release the energizing circuitfor the relay IIiI-ID from.

(+), and including front contact I34 of relay I4YGP, back contact 89 ofrelay I3HDP, front contact 90 of relay I3TR, line wire M to the signallocation of Fig. 1D, front contact 92 of relay IIi'I'R, back contact 93of relay IIiCK, windings of relay IGHD, front-contact H of relay IBTR,line wire 22 to the'signal location of Fig. .14, front contact 23 oftrack relay I3TR, front contact- I of relay I4YGP,, to The-current whichflows in this circuit energizes the relay IBHD in such a direction as topermit the operation of the signal I6B to a clear or green indicatingposiof the slow acting relay IHDP energy is applied to a circuit forenergizing the operating magnet of the signal I2 by a circuit closedfrom and including back contact I28 of relay SYGP, front contact 63 ofrelay ITR, line wire 64 to the signal location of Fig. 13, back contact65 of relay IZ'I'R, operating winding of signal I2, back contact I21 ofrelay II S, back contact ll) of relay IIYGP, front contact II of relay-ITR, line wire I2 to the signal location of Fig. 1A,

front contact I3 of relay lAS, front contact I4. .of relay i'I'R, frontcontact 15 of relay 9TB,

.back contact It of relay 'IGZP, back contact'li of relay IHDP, windingsofrelay CK, back contact I28 of relay 8YGP, to The energy which flows inthis circuit is of such a direction as to cause the signal I2 to beoperated to its caution indicating position. The energy which flows inthis circuit also energizes the relay 'ICK included in series thuspicking up front contact 62 to prepare the circuit for the relay IBKwhich of course cannot be energized so long as the relay ItGZP is pickedup. However, it might be desirable to note that the circuit for therelay 'IBK has no energy applied to it at this time and cannot receiveenergy until the relay IIBK picks up and closes front contact I29 inFig. 1B.

The operation of the signal I2 to a caution or yellow indicatingposition completes an energizing circuit for the relay I2YGP from andincluding contact 54 in an operated position and front contact I30 ofrelay IITR. Ifhe picking up of the relay I2YGP completes an energizingcircuit for the operating winding of signal I4 from and includingcontacts 52 and 63 of signal II in normal positions, front contact I3Iof relay I 2YGP, back contact 85 of relay IIYGP, back contact 84 ofrelay'I IS, front contact 83 of relay IITR, line wire '82 to the signallocation of Fig.

tion by reason of an energizing circuit similar to that pointed out inconnection with the signal IA.

From the above description, it will be observed that each signal iscleared dependent upon its opposing signal being at stop. For example,the signal I2 has an energizing circuit which is closed only providingthe relay lGZP is deenergized closing back contact I6, which of courseinsures that the front contact H02 will be open holding the signals IAand 1B at stop. Similarly, the energizing circuit for the signal I8includes contacts closed only providing the signal I I is at stop andproviding the signal i2 is indicating caution. Itcan thusbe seen thatthe signal clearing tumbledown circuits build up from the remote orleaving end of the route to be established and thus permits the clearingof the head-block signal only after all of the opposing signals havebeen checked at stop during this reversal in direction of the signalclearing tumble-down circuits. It will be noted that the traffic lockingrelays, such as relays IIBK and I2BK, are all deenergized thus causingthe intermediate signals to be 11- luminated to give the properindications in accordance with the established control. Both of thesignals 8A and 8B are illuminated by reason of the closure of backcontacts I36 and I3? of relays 'IHDP and IBK respectively. These signals8A and 8B are of course shown as indicating stop, but it is to beunderstood that they may be manually controlled to indicate caution orclear as the case may be in accordance with the manual control dependentupon suitable auto-.

Detailed operations involved during the passage of a westbound trainwill not be pointed out in detail, since such operations will beunderstood by analogy to the operations involved with regard to thepassage of an eastbound train. It will of course be recognized that eachtime the westbound train proceeds past a signal location that theassociated directional stick relay is picked up and energy is applied tothe signal control circuit in the rear to allow for following'tra'inmovements. When the train has entirely passed through the single trackstretch, the signal clearing tumble-down circuits will be reenergizedforactuating the signals I2 and It to their caution and clear positionsrespectively, assuming that the signal 8 is at stop.

Also, assuming that the manual control of relay IGGZ has been restoredto its deenergized p0- sition, the relay IGGZP is released so that thetraffic locking tumble-down circuits including relays I3BK, IIBK and IBKare successively energized to restore the intermediate signals to theirnormal dark conditions, and thus cause the motor car indicator of Fig.1A to be energized through front contact I38 of relay IBK. Thisenergization of the motor car indicator of course advises workmen thatthey may proceed into the single track stretch because there is noopposing direction of traflic established.

More specifically, the relay I3BK is energized by a circuit closed fromandincluding front contact I34 of relay IYGP, windings of relay I3BK,front contact of relay IlYGP, front contact 26 of relay I3TR, line wire21 to the signal locationof Fig. 1D, front contact 28 of relay ISAS,front contact 29 of. relay IBTR, front contact 30 of relay I'ITR, backcontact 3| of relay IGGZP, front contact 32 of relay ISHDP, frontcontact 2I of relay IGTR, line wire 22 to the sig nal location of Fig.1C, front contact 23 of track relaiy I 3TB, front contact I35 of relayMYGP, to

The picking up of the relay I3BK in turn causes the energization of therelay IIBK by reason of a circuit closed from and including contact 35of signal I4 in a normal position and contact 36 in an operatedposition, front contact 39 of relay IiBK, front contact 40 of trackrelay TR, line wire II to the signal location of Fig. 113, front contact42 of track relay HTR, windings of relay IIBK, front contact 41 of relayI2YGP, front contact 45 of relay I ITR, line wire 46 to the signallocation of Fig. 16, front contact 41 of track relay TR, back contact 48of relay HS, front contact 49 of relay IAYGP, front contact I 39 ofrelay ISBK, to (-l.

Relay IBK is energized by reason of a circuit closed from and includingback contact I26 of relay BYGP, front contact 83 of relay ITR, line wire64 to the signal location of Fig. 13, front contact 65 of relay I2'I'R,front contact I29 of.

- relay IIBK, front contact 5'! of relay I2YGP,

backcontact 58 of relay I2S, front contact 59 of relay I2TR, line wire60 to the signal location of Fig. 1A, front contact SI of relay TITR,front contact 62 of relay ICK, windings of relay IBK, back contact I28-0! relay BYGP, to

Summary of tumble-down circuits-With reference to the drawings, it willbe seen that the signal clearing tumble-down circuits for oppositedirections are interlocked with respect to each other. For example, thesignal II is controlled through a back contact 44 of relay I2YGP, whilethe signal I2 is controlled through a back con tact III of relay IIYGP.By reason of these contacts the signal clearing tumble-down circuitscircuit at the other end of the block. However,-

this is not true with respect to the end track sec- .tions between theheadblock signals and the first intermediate signal location. Forexample, the tramc locking relay I2BK is controlled from the signallocation of Fig. 1A, but its energy is supplied from its own signallocation, as will readily be seen by a study of its detailed circuitpreviously described. Likewise, the trafllc lockin relay IBK receivesenergy from its own signal location although its circuit is controlledfrom the signal location of Fig. 1B in accordance with the energizationof the relay I IBK under the proper conditions, as previously described.Thus, the trafiic locking tumble-down circuits for the end sections orblocks of the single track stretch are not symmetrical with respect tothe intermediate track sections. However, it should be understood thatthere may be more than the one intermediate track section whenconditions require it. For this reason, it should be understood thatother intermediate signal locations might be'provided by arranging thecontrols for such signals as disclosed for the opposing signals II andII. If the signal location of Fig. 1C is desired to be 01- the doubleintermediate type, then an additional signal I3 can be provided forgoverning trafllc towards the siding B with its operating windingreplacing the relay I3HD and its associated relay I3YGP (not shown)taking the place of the relay I3HDP. In other words, such a signal wouldhave the same relationship to its siding as the signal I2 has withrespect to the siding A.

Modification of Fig. 2.This Fig. 2 illustrates a modification of theinvention as shown in Fig. 13 by changing the approach lighting controlof the signals II and I2 to track circuit controlled contacts I40 and-l4I of relays I 2TB and IITR respectively. In other words, the signalII is illuminated only when a train approaches such signal anddeenergizes the track relay I2TR.- This same principle of approachlighting may be applied to each of the other approach lighted signals inthe same manner as shown for these signals II and I2, but which hasnotbeen shown applied to the other figures for the same of simplicity.The signal clearing tumble-down circuits and the trafllc lockingcircuits for this form of the invention are exactly the same as shown inFig. 1B. 0 However, 'two motor car indicators for opposite directions oftrafllo, as indicated by arrows with the respective indicators, areprovided so that it is safe for a motor car to proceed over the trackwayonly when both such indicators are illumi- 65 nated. The eastboundindicator is controlled by front contacts I42 and I43 of the relaysIIYGP and II BK respectively; while the westbound indicator iscontrolled by front contacts I 44 and I45 of the relays I2YGP and I2BKrespectively.

With reference to the preceding description for an understanding of theoperation of the various tumble-down circuits, it will be understoodthat when a route is established for eastbound traffic, the relay IIYGPwill be picked up closing front contact I42 but the relay I2BK will bedeenera 17 gized so that only the the arrow pointed to the right isilluminated. This informs the motor car operator, or other workmen, thata route has been established and that it is unsafe for motor caroperation, but the indicator which still remains illuminated advises thedirection in which traflic is established, so that the direction fromwhich a train should be expected will be known. It will be obvious thatwhen the train has actually passed the signal location both indicatorlamps will be extinguished until such train has passed beyond the nextintermediate signal location or has left the single track stretchentirely, as the case may be, at which time the lamps will beilluminated in accordance with the traflic conditions just discussed. Itis believed that the-indication displayed by these indicators fortraiiic in the opposite direction will be readily understood.

As previously mentioned, these indicators need not necessarily belocated at the signal location itself but may be located at a suitablepoint in accordance with the particular curvature of the track, or thelike, requiring a different location. For example, such indicators mightbe located in the building adjacent a highway crossing, so

as to advise the crossing fiagman as to when to expect a train.

Having thus described a signaling system as one specific embodiment ofthe present invention, it is desired to be understood that this form isselected to facilitate in the disclosure of the invention rather than tolimit the number of forms it may assume. It is to be further understoodthat various modifications, adaptations and alterations may be appliedto the specific form shown to meet the requirements of practice withoutin any manner departingfrom the spirit or scope as limited by theappended claims.

What I claim is:

1. In a manually-controlled block signal system for single trackrailroads, a stretch of single track having a head-block signal at eachend and intermediate signals at intervals governing train movement inopposite directions into and through said stretch of single track, aseries of line circuits for each direction of trafic, a trafiicdirection locking relay for each direction associated with each signaland energized alternately by an associated line circuit dependent uponthe direction of trafic established, approach lighting means for eachintermediate signal responsive to the deenergizatlon of oath of theassociated traflic direction locking relays for opposite directions oftraffic, and manually controlled means governed by said series of linecircuits and said tramc direction locking relays for governing theclearing of signals for train movement into and through said singletrack stretch for either selected direction of traflic.

2. In a system of centralized tramc control for single track railroads,a stretch of single track between the ends of passing sidings and havingsignals at intervals governing train movement into and through saidstretch in opposite directions, a signal control relay for governing theindications of each signal, a trafiic-direction locking relay associatedwith each signal, two series of interlocked line circuits one for eachdirection of trafiic for governing the energization of the signalcontrol relays of the signals for only one direction of tramc at a timeand also the energization of said tramc direction locl'ing relaysassociated with the signals for the opposite direction of traiiic, andmanually controlledmeans motor car'indicator with governed by saidtraflic direction locking relays for the opposing signals at the ends ofsaid single track stretch for governing the clearing of said signals foreither selected direction of traiiic. 3. In a system of centralizedtraflic control for single track railroads, a stretch of single trackhaving signals at intervals governing train movement into and throughsaid stretch in opposite directions, a signal control relay forgoverning the indications of each signal, a series of line circuits foreach direction of traflic for energizing the signal control relays ofthe signals governing train movement in a corresponding direction, meansfor interlocking said series of line circuits for opposite directions oftrafiicto permit the clearing of signals for only one direction oftraffic at a time, auxiliary tramc direction locking relay meansgoverned by the continuity of each series oi line circuits when noteffective to energige signal control relays, and means manuallycontrolled irom a distant control ofiice and dependent upon thecondition of said trams direction locking means for governing saidseries of line circuits to clear signals for the movement tlons, asignal control relay associated with each I of said signals forgoverning its indications, two series of interlocked line circuits onefor each direction for energizing the signal control relays of thesignals for only one direction of traiiic at a time, trafilc directionlocking means for each end of the stretch responsive to the continuity'of the series of line circuits relating to the direction of trafficaway from that end even though that" series of line circuits is not theneffective to control the energization of the signal control relays forthat direction of trafilc, and means for each end of said stretchmanually controlled from a distant control omce and governed by theassociated trafiic direction locking means for controlling the clearingof the associated head-block s gnal and the continuity of the series ofline circuits for the opposite direction of traffic.

5. In a signaling system for single track railroads, a stretch of singletrack between the ends of two passing sidings, head-block signals ateach end of the stretch for governingtraiiic into the stretch at thatend, intermediate signals located at intervals through the stretch forgoverning trafic in both directions, manually controlled line circuitmeans for causing the head-block signal to be cleared at either selectedand of the stretch and also causing the clearing of the intermediatesignals for the corresponding direction, and motor car indicatorsassociated with each end of the stretch and each being governed by saidline circult means to indicate at its end of the stretch intermediatesignals located at the end-s of the sections through the stretch forgoverning tr'afli'c in both directions, line circuit means for said oftrains into and through said stretch in eitherstretch including threeline: wires individual to each track section, manually controlled meansat the ends of the stretch for acting over said line wires to cause saidsignals to be cleared for either selected direction only after thesignals for the opposing direction have been checked at stop, said meansalso clearing the head-block signal for the corresponding direction,motor car indi line circuit means associated with said signals andmanually governable for causing the clear control of the head-blocksignal at either. selected end of the stretch and the intermediatesignals for the corresponding direction, approach lighting control meansassociated with each intermediate signal for illuminating that signalwhen a train is in approach thereto, a motor car indicator associatedwith each head-block and intermediate signal, and control means for saidmotor car indicators governed by said line circuit means to cause saidindicators for the intermediate signals to indicate the establisheddirection of traffic upon the manual control of said line circuitmeansand to cause the motor car indicator at the leaving end of thestretch to indicate the establishment of an opposing direction oftraffic in response to the manual control of said line circuit means forclearing the head-block signal at the opposite end of the stretch,whereby the establishment of the trafilc direction in a stretch ofsingle track is indicated for the benefit of workmen prior to theentrance of a train into the stretch.

8. In a signaling system for a single track railroad having a stretch ofsingle track between two passing sidings, head-block signals at each endof the stretch for governing the entrance oftraffic into the-stretch,intermediate signals located at intervals through the'stretch forgoverning trafiic in both directions and dividing said stretch intosections. line circuit means associated with said stretch of singletrack and manually governable for clearing the head-block signal ateither end of the stretch and the intermediate signals for thecorresponding direction, said line circuit means being so organized asto require all opposing signals to be placed at stop before the signalsfor the selected direction can be cleared, said line circuit means beingeffective to prevent manual control of either end of the stretch tointerrupt an established direction of trafllc when the manual control atthe opposite end of the stretch is effective to establish traffic, saidline circuit means comprising two line wires and a common line wire foreach track section of the stretch, and circuit means controlled by saidline wires for each track section for indicating adjacent each signallocation whether or not said line circuit means is being manuallygoverned.

. 9. In a signaling system for a, stretch of single track between twopas-sing sidings, head-block signals at each end of the stretch forgoverning trafilc into the stretch at that end, intermediate sig alsnormally unilluminated and located at 20 intermediate 'polnts throughthe stretch for governing opposite directions of'trafiic, line circuitmeans associated with said stretch and normally conditioned forgoverning said intermediate signals for one direction or the other toclear conditions, manually controlled means at the ends of said stretcheffective to control said line circuit means for governing saidintermediate signals to clear conditions for either selected directionof traflic followed by the clearing of the head-block signal for thecorresponding direction, said control of said line circuit means beingdistinctive while said manually controlled means is active, meansassociated with each intermediate signal for causing that signal to beilluminated during the distinctive control of said line circuit means,and motor car indicator means associated with each end of the stretchand distinctively controlled by the distinctive condition of said linecircuit means whenever the head-block signal at the opposite end of thestretch is cleared to thereby indicate the establishment of traffictoward its end.

' 10. In a railroad signaling system for stretches of single track overwhich trafiic can move in either directionbetween two passing sidings,light signals located at intervals through said stretch for governingboth directions of traffic, line circuit means associated with saidstretch and manually controlled for causing the signals to beconditioned to indicate clear for only one direction of traffic at atime and acting to maintain the controlled condition of the signals forthe last established direction of trailic although the manual control isremoved, and means responsive to the manual control of said line.circuit means at either selected end of the stretch for lighting all ofthe signals in the stretch and preventing manual control of said linecircuit means at the other end of the stretch.

11. In a signaling system for single track railroads, a stretch ofsingle track extending between the ends of two passing sidings anddivided into track sections, head-block signals at each end of thestretch for governing traffic into the stretch, intermediate signalslocated at intervals through the stretch corresponding to the ends ofthe track sections for governing traffic in opposite directions, saidhead-block and intermediate signals being of the light signal type, linecircuit means for said stretch of single track comprising a signalclearing tumble-down circuit and a traffic locking tumble-down circuitfor each direction of traffic imposed upon three line wires individualto each track section, said tumbledown circuits receiving energy at theends of the stretch and being interlocked to normally provide for theenergization of the signal clearing tumble -down circuit for the lastdirection of traffic and for the energization of the trafiic lockingtumble-down circuit for the opposite di-,

rection, manually controlled means at each end of the stretch forcausing the deenergization of the particular signal clearing or trafficlocking tumble-down circuit then receiving energy from that end of thestretch to thereby cause thesignal clearing tumble-down circuits for thesignals governing traflic away from that end of 'the stretch to beenergizedto clear such signals while of both traffic locking bothdirections of tramc, signal control relay means associated with eachsignal, signal clearing tumble-down circuits for each direction oftraflic comprising successive link circuits, one for "each of saidsignal control relays, said link circuits for opposite directions oftrafiic being interlocked at each signal location to permit; theenergization of the tumble-down circuits for only one direction or theother at the'same time, a tramc condition relay associated with eachsignal, traffic condition tumble-down circuits for each direction oftraffic including a link circuit for each traflic condition relay andeach of the link circuits being controlled through a front contact ofthe signalcontrol relay means for the opposite direction, whereby thesignal clearing tumbledown circuits are-energized for only one directionat a time and whereby the traffic condition tumble-down circuits can beenergized for only the opposite direction, manually controlled means ateach end of the stretch effective when rendered active to deenergize thesignal clearing tumbledown circuit and the tratfic condition tumbledown"circuit governing the signals which govern trafiic towards its end ofthe stretch, said manually controlled means being capable of beingrendered active only if either the signal clearing tumble-down circuitor the traific condition tumble-down circuit for traffic away from thatend is energized, and means for illuminating each of said signals whenboth of the trafiic condition relays for that signal location arecleenergized.

13. In a railroad signaling system for stretches of single track overwhich trafiic can move in either direction between two passing sidings,signals located at intervals through said'stretch for governing tramc inboth directions, control relay means associated with each signalandcontrolled in accordance with the control relay means associated withthe signal next in advance for the same direction and in accordance withthe trafic conditions in the intervening section to thereby provide aso-called tumble-down circuit,

meansassociated with each signal for causing that signal to indicateclear only when the associated control relay means is energized, meansat each signal location including contacts of the control relay means atthat signal for interlocking said tumble-down circuits for oppositedirections to permit energization of the relay means for only onedirection at a time, manually controlled means at each end of thestretch effective when rendered active to deenergize the tumbledowncircuit for the signals governing traflic towards its end to therebypermit energization of the tumble-down circuit for the oppositedirection for clearing the signals away from that siding end, andcircuit means associated with said stretch and rendered effective whenthe manually controlled means at one end of the stretch is active toprevent the manually con trolled means at the other end of the stretchfrom also being rendered active, whereby said signals 'associatedwithsaid stretch of track can be cleared for only one direction at a timeand whereby a direction of trafi'ic established at one end of thestretch by manual control cannot be interrupted by independent manualcontrol at the opposite end of the stretch.

14. In a signaling system for railroads, a stretch of single trackbetween two passing sidings divided into a, plurality of track sections."signals located at the section ends for governing trafiic in bothdirections through the corresponding sections, signal control relaymeans associated with each signal and capable of clearing its signalonly when such relay means is energized, line circuit means forrendering each signal control relay means energizable in accordance withthe traffic conditions and the condition of the signal control relay forthe signal next in advance for the same direction of traffic to therebyprovide a socalled tumble-down circuit organization for each directionof trafic, said tumble-down circuits for each direction of trafilc'including at each signal location a contact opened when the signalcontrol relay means for the opposite direction of traflic is energizedwhereby the tumble-down circuits for only one direction of trafllc canbe energized at a time, trafic controlling circuits extending throughsaid stretch, manually controlled means at each end of the stretch, eachbeing energizable independently in response to manual control from acentral omce, traific controlling relay means at each end of the stretchrendered efiective in response to the associated manually controlledmeans to deenergize the tumble-down circuits for the signals governingtraffic toward that end to thereby permit the clearing of the signalsgoverning traffic away from that end of the stretch, said trafficcontrolling relay means being effective to act through said traiiiccontrolling circuits to prevent the response of the trafic controllingrelay means at THO J. JUDGE.

